I think you need to disconnect power after you go in recovery mode

RESET BATTERY PERCENTAGE

Unplug the device from the AC adapter and power it down completely.
Press Escape+Refresh+Power keys simultaneously to invoke recovery mode. (you should be greeted with a screen that says “Chrome OS is missing or damaged. It’s okay, nothing is broken. Do not press any other keys)
Now, plug the AC adapter back in and leave the device as is. Do not power down or close the lid.
Leave the Chromebooks plugged in for 6 hours to allow the battery to recalibrate and take a full charge.
While still plugged in, hold the power button and power down the device.
Leaving the device plugged in, power it back up and you should see the battery level at full or close to it.
Unplug the Chromebook and you’re all set. The battery should be back to its normal self and the indicator should reflect the full charge.